silicon heating furnace

ABSTRACT

The silicon heating furnace is constructed by combining two semi-cylindrical furnaces. Each of the semi-cylindrical furnaces has a semi-cylindrical housing, an insulator, heaters, and an isothermal material. Radial direction separation preventing members are arranged in inner side of both ends of circumferential direction of the housing to prevent a separation of the insulator to radial direction. End face of circumferential direction covers are fixed on the radial direction separation preventing members to cover the end faces of circumferential direction of the insulator. Cooling pipes for end faces of circumferential direction through which cooling water passed are arranged between the end faces of circumferential direction of the insulator and the end face of circumferential direction covers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a silicon heating furnace for heating araw material silicon in a method that breaking the raw material siliconinto pieces by quenching after heating. Particularly, the presentinvention relates to a silicon heating furnace which is constructed bycombining two semi-cylindrical furnaces.

2. Description of the Related Art

Silicon wafers for semiconductors are produced through steps that (a) astep for producing a raw material silicon, (b) a step for producing asingle-crystal silicon ingot (substantially cylindrical) from the rawmaterial silicon, and (c) a step for slicing the single-crystal siliconingot into discs.

For the step (b), well-known “Czochralski Method” (to be referred to asthe CZ method) is generally used. The CZ method has some steps that astep for heat-melting the raw material silicon in a crucible, a step fordipping a rod of the single-crystal silicon (a seed) into the moltensilicon, and a step for pulling the rod upwards and rotating at the sametime. For the CZ method, the raw material silicon is required to bebroken into pieces to be easily thrown into the crucible and to bemelted in short time.

Because of such requests, some kinds of “method for breaking the rawmaterial silicon effectively” have been developed; for examples, seeJapanese Patent Laid-Open No. H10-15822 (Document 1). A breaking methoddescribed in the Document 1 has a step for heating a raw materialsilicon (polycrystalline silicon) rod up to 440 to 800° C., a step forgenerating cracks by quenching to less than 100° C., and a step forbreaking into pieces by impact.

According to this “method for breaking the raw material silicon”, theraw material silicon is broken easily by hitting the raw materialsilicon against other raw material silicon, because internal cracks ofthe raw material silicon are generated by heating. Accordingly, it isnot necessary to use hammers or the like for breaking the raw materialsilicon. This results that hard work is dispensed and contamination ofthe raw material silicon with hammers or the like is avoided. Inheating, however, it is necessary to heat the raw material silicon in aheating furnace; there is another problem that the raw material siliconis contaminated with metal impurities diffused from constructionmaterial of the heating furnace.

Then a “heating furnace” which is described in the Document 2 (JapanesePatent Laid-Open No. 2005-288336) is developed. The “heating furnace”has a cylindrical main body which is constructed with twosemi-cylindrical housings. Inner surface of the main body is coveredwith a coat of quartz glass and parting surface of each housing iscovered with a coat of titanium.

According to the “heating furnace” described in Document 2, covering theinner surface of the main body and the parting surface of each housingwith the coat, the diffusion of the metal impurities into the heatingfurnace and the contamination can be avoided. And by separating one ofthe housing from the other, a wide hatch for taking out and putting intothe raw material silicon can be made.

However, because each of the housings of the “heating furnace” has a“rectangular” opening, a longer side of the “rectangular” opening can bedeformed easily with heat expansion. The deformation of the longer sidewith heat expansion makes a gap at a joining surface of each of thehousings. Heat in the furnace leaks through the gap with remarkabledecrease of heat efficiency.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a silicon heatingfurnace which can avoid the contamination of the raw material siliconand the decrease of heat efficiency with the heat expansion.

In accordance with an aspect of the present invention, a silicon heatingfurnace 10 having a heating chamber S1 for containing raw materialsilicon 12 to be heated, comprising:

two semi-cylindrical furnaces 26 a, 26 b constructing the cylindricalsilicon heating furnace by combining each other:

each of the semi-cylindrical furnaces 26 a,26 b having:

-   -   a semi-cylindrical housing 34;    -   a semi-cylindrical insulator 36 arranged in inner side of the        housing 34;    -   a heater 38 arranged in inner side of the insulator 36;    -   a semi-cylindrical isothermal material 42 made of heat-resistant        glass, and arranged in inner side of the heater 38 and heated by        the heater 38, and constituting an inner wall of the heating        chamber S1;    -   radial direction separation preventing members 44 arranged in        inner side of both ends of circumferential direction of the        housing 34, and preventing a separation of the insulator 36 to        radial direction by contacting at end faces of circumferential        direction 36 a of the insulator 36;    -   end face of circumferential direction covers 46 fixed on the        radial direction separation preventing members 44, and covering        the end faces of circumferential direction 36 a of the insulator        36; and    -   cooling pipes for end faces of circumferential direction 48        through which cooling water passed arranged between the end        faces of circumferential direction 36 a of the insulator 36 and        the end face of circumferential direction covers 46.

According to the present invention, because the insulator 36 is arrangedbetween the housing 34 and the heater 38, the heat from the heater 38 isprevented from directly transferring to the housing 34 to keep a shapeof the housing 34 against the strain of heat expansion. Further, becausethe circumferential direction cooling pipes 48 are arranged between theend faces of circumferential direction 36 a of the insulator 36 and theend face of circumferential direction covers 46, the end faces ofcircumferential direction 36 a of the insulator 36 can be cooled by thecooling pipes for the end face of circumferential direction 48 to keep ashape at the circumferential edge of the housing 34 against the strainof heat expansion.

Furthermore, covering the inner surface 36 c of the insulator 36 withthe isothermal material 42 and covering the end faces of circumferentialdirection 36 a of the insulator 36 with the end face of circumferentialdirection covers 46 cause metal impurities diffused from the insulator36 not to be diffused into the heating chamber S1. And using theisothermal material 42 made of heat-resistant glass causes metalimpurities not to be diffused from the isothermal material 42 itselfinto the heating chamber S1.

Both of the end face of circumferential direction covers 46 and thecooling pipes for the end face of circumferential direction 48 may bemade of titanium and may be welded each other.

Using titanium which is hard to generate heat diffusion for the end faceof circumferential direction covers 46 and the cooling pipes for the endface of circumferential direction 48 prevents the metal impurities fromdiffusing. And welding the end face of circumferential direction covers46 and the cooling pipes for the end face of circumferential direction48 causes the end face of circumferential direction covers 46 to becooled effectively by the cooling pipes 48 and the cooling pipes 48 tobe set easily by fixing the end face of circumferential direction covers46 to the radial direction separation preventing members 44.

Seals 40 made of string of quartz fibers may be arranged toward axialdirection between an inner surface of the end of circumferentialdirection of the insulator 36 and an outer surface of the end ofcircumferential direction of the isotheimal material 42.

Sealing a clearance S3 between the insulator 36 and the isothermalmaterial 42 with the seals 40 of string of quartz fibers causes themetal impurities diffused from the inner surface of the insulator 36 tobe prevented from diffusing into the heating chamber S1 through theclearance S3.

Each of the two semi-cylindrical furnaces 26 a, 26 b may comprise axialdirection separation preventing members 50 arranged at both ends ofaxial direction of the housing 34, preventing the insulator from beingseparated toward the axial direction by contacting to both end faces ofaxial direction 36 b; supports 54 a, 54 b having fixing plates 108fitted to the axial direction separation preventing members 50 andsupporting plate 110 a supporting the end of axial direction of theisothermal material 42; side panel cooling pipes 56 through whichcooling water pass; side wall members 58 made of heat-resistant glass,covering the end faces of axial direction 36 b and constituting innerwalls of the heating chamber S1.

Arranging the side panel cooling pipes 56 as to contact to the supports54 a, 54 b causes the supports 54 a, 54 b to be cooled and the axialdirection separation preventing members 50 to which the supports 54 a,54 b are attached to be cooled. Furthermore, the end faces of axialdirection 36 b of the insulator 36 which contact to the axial directionseparation preventing members 50 are also cooled.

Covering the end faces of axial direction 36 b of the insulator 36 withthe axial direction separation preventing members 50 and the side wallmembers 58 causes the metal impurities differed from the insulator 36 tobe prevented from diffusing to the heating chamber S1.

The supports 54 a, 54 b and the side panel cooling pipes 56 may be madeof titanium and welded each other.

In the present invention, by constructing the supports 54 a, 54 b andthe side panel cooling pipes 56 with titanium which is difficult todiffuse, the diffusion of the metal impurities from these parts into theheating chamber S1 is prevented. And by welding the supports 54 a, 54 band the side panel cooling pipes 56, the supports 54 a, 54 b are wellcooled and arranged easily only with fixing the supports 54 a, 54 b tothe axial direction separation preventing members 50.

According to the present invention, the heat of the heater 38 isprevented from transferring directly to the housing 34 by the insulator36. Furthermore, the end faces of circumferential direction 36 a of theinsulator 36 are cooled efficiently by the cooling pipes for the endfaces of circumferential direction 48. Therefore, the housing 34 isprevented from being high temperature. Especially, the end ofcircumferential direction of the housing 34 is prevented from deformingby heat expansion and generating a gap at the joint surface between thetwo semi-cylindrical furnaces 26 a, 26 b is avoided. As a result,preventing a leak of the heat of the heating chamber S1 through the gapcauses a decreasing of the heating efficiency with the deforming by heatexpansion to be avoided.

Furthermore, covering the inner surface 36 c of the insulator 36 withthe isothermal material 42 and covering the end faces of circumferentialdirection 36 a of the insulator 36 with the end face of circumferentialdirection covers 46 cause the metal impurities diffused from theinsulator 36 not to be diffused into the heating chamber S1. And the rawmaterial silicon 12 heated in the heating chamber S1 is prevented frombeing contaminated with the metal impurities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a silicon heating furnace.

FIG. 2 is a side view of a silicon heating furnace.

FIG. 3 is a sectional view of an opened silicon heating furnace.

FIG. 4 is an enlarged view of an end face of axial direction of aparting surface of a silicon heating furnace.

FIG. 5 is a schematic view of a silicon heating furnace in-use.

FIG. 6 is an exploded perspective view of a semi-cylindrical furnace(radial direction)

FIG. 7 is an exploded perspective view of a semi-cylindrical furnace(axial direction)

FIG. 8 is a perspective view of an insulator fixing structure.

FIG. 9 is a perspective view of a fixing structure of a cover for an endface of circumferential direction and cooling pipes for an end face ofcircumferential direction.

FIG. 10 is a perspective view of a fixing structure of a fitting plate.

FIG. 11 is a perspective view of a fixing structure of supports and sidepanel cooing pipes.

FIG. 12 is an enlarged view of “XII” part of FIG. 11.

FIG. 13 is a perspective view of a fixing structure of a side wallmember and a cover.

FIG. 14 is an enlarged view of “XIV” part of FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a perspective view of a silicon heating furnace 10 inaccordance with an embodiment of the present invention. FIG. 2 is a sideview of the silicon heating furnace 10. FIG. 3 is a sectional view ofthe opened silicon heating furnace 10. FIG. 4 is an enlarged view of anend face of axial direction of a parting surface of the silicon heatingfurnace 10. And FIG. 5 is a schematic view of the silicon heatingfurnace 10 in-use.

The silicon heating furnace 10 heats a raw material silicon 12 up tohigh temperatures of 440-1000° C. in a method for breaking the rawmaterial silicon by quenching after heating. As shown in FIG. 5, thesilicon heating furnace 10 is used in a combination with a cooling watertank 14 for quenching the raw material silicon 12 and a conveyer 16 forconveying the raw material silicon 12.

The conveyer 16 (FIG. 5) includes a basket 18 for being loaded the rawmaterial silicon 12, a wire 20 for suspending the basket 18, a winch 22for winding and unreeling the wire 20, and travelling device 24 fortravelling the winch 22 in a horizontal direction. For quenching the rawmaterial silicon 12 after heating, the basket 18 which is loaded the rawmaterial silicon 12 is conveyed into the silicon heating furnace 10 atthe beginning. Then the basket 18 is immersed into the water of thecooling water tank 14.

The basket 18 (FIG. 5) of the conveyer 16 includes a pair of side plates18 a arranged to face each other, and pipes 18 b bridged between theside plates 18 a and loaded the raw material silicon 12. Each of theside plates 18 a has a wire connector 18 c on its upper side. The wire20 is connected to the wire connectors 18 c. A size of a heating chamberS1 and an open-close mechanism of a opening A of the silicon heatingfurnace 10 is designed in consideration of the relation with the basket18 and wire 20.

The silicon heating furnace 10 (FIG. 1-5) is a cylindrical furnace whichhas a heating chamber S1 (FIG. 5) for being placed the basket 18. Thesilicon heating furnace 10 is constructed with two semi-cylindricalfurnaces 26 a, 26 b with using hinges 28 (FIG. 3). In use of the siliconheating furnace 10, as shown in FIG. 5, one semi-cylindrical furnace 26a is fixed to a support 30, and a hydraulic cylinder 32 is fixed to theother semi-cylindrical furnace 26 b. The opening between the twosemi-cylindrical furnaces 26 a, 26 b the opening A) is opened and closedwith the hydraulic cylinder 32.

Each of the semi-cylindrical furnaces 26 a, 26 b has a semi-cylindricalhousing 34, as shown in FIGS. 1, 3, and 4. An insulator 36, heaters 38,seals 40, and a isothermal material 42 are built onto an inside of thehousing 34 in this order, as shown in FIG. 6. Radial directionseparation preventing members 44 for preventing the insulator 36 fromseparating to the radial direction are arranged on each inner surface ofboth end of circumferential direction. And end face of circumferentialdirection covers 46 for covering both end faces of circumferentialdirection of the insulator 36 are fixed to the Radial directionseparation preventing members 44. Cooling pipes for end face ofcircumferential direction 48 are arranged between the end faces ofcircumferential direction 36 a of the insulator 36 and each end face ofcircumferential direction covers 46.

Axial direction separation preventing members 50 for preventing theinsulator 36 from separating to the axial direction are fixed to bothends of axial direction of the housings 34, as shown in FIG. 7. Fittingplates 52 and two kinds of supports 54 a, 54 b are fixed on the face ofthe axial direction separation preventing members 50. Side panel coolingpipes 56 are abut to the supports 54 a, 54 b. Furthermore, side wallmembers 58 for covering the end faces of axial direction 36 b of theinsulator 36 and the end faces of axial direction 42 b of the isothermalmaterial 42 from face side of the axial direction separation preventingmembers 50 and being inner wall of the heating chamber S1 are fixed onthe face of the fitting plates 52 with covers 60 by means of fixingbrackets 62.

On outer surface of one end of circumferential direction of the housing34, as shown in FIG. 3, square pipes 64 are arranged along to edges ofcircumferential direction of the housings 34. The pipe 64 for onesemi-cylindrical furnace 26 a and the pipe 64 for the othersemi-cylindrical furnace 26 b are connected each other by the hinges 28.And L-shaped reinforcing bar 66 for preventing the housing 34 fromdeforming is fixed to each of the pipes 64.

Hereinafter, each of parts for the silicon heating furnace 10 isexplained in detail with reference to figures.

The housings 34 construct the outer wall of each of semi-cylindricalfurnaces 26 a, 26 b. The housings 34 are made of semi-cylindricallybended metal such as stainless steel or the like. As shown in FIG. 8 andFIG. 9, cut-out 68 through which both ends 48 c, 48 d of the coolingpipes for end face of circumferential direction 48 pass are arranged atboth edge of circumferential direction of one end of axial direction ofthe housing 34. As shown in FIG. 6 and FIG. 8, radial directionseparation preventing members 44 are fixed by weld or screws at innersurfaces of both ends of circumferential direction of the housing 34,not at the cut-out 68.

The radial direction separation prevention members 44, as shown in FIG.8, prevent the insulator 36 from separating to radial direction bycontacting to the end faces of circumferential direction 36 a of theinsulator 36. Each of the radial direction separation prevention members44 includes a housing fixing piece 44 a which is fixed to the housing 34and a cover fixing piece 44 b to which the end face of circumferentialdirection cover 46 is fixed (FIG. 9). Therefore, each of the radialdirection separation prevention members 44 has “L” shape. Several screwholes 72 for screws 70 (FIG. 9) are arranged on the cover fixing piece44 b at specified intervals in a longitudinal direction.

In the state that the housing fixing piece 44 a is fixed to the housing34, a space S2 for being placed the end face of circumferentialdirection cover 46 and a head portion 70 a of the screw 70 between thesurface (to be fixed) of the cover fixing piece 44 b and the end face ofcircumferential direction 34 a of the housing 34. Therefore, the endface of circumferential direction cover 46 and the head portion 70 a ofthe screw 70 do not stick out from the end face of circumferentialdirection 34 a of the housing 34, and do not make the assembling the twosemi-cylindrical furnaces 26 a, 26 b to one cylinder difficult.

The insulator 36 prevents the heat of the heaters 38 from transferringdirectly to the housings 34. As shown in FIG. 6, the insulator 36 isconstructed by making a heat-resistant insulating material such asalumina fiber cotton or the like semi-cylindrical shape. On outersurfaces of both ends of circumference direction of the insulator 36, asshown in FIG. 6 and FIG. 8, steps 74 a for being arranged the housingfixing pieces 44 a of the radial direction separation preventing members44 are formed. On the outer surfaces of both ends of axial direction ofthe insulator 36, steps 74 b for being arranged contact pieces 84 (FIG.7) of the axial direction separation preventing members 50 are formed.On the end faces of circumferential direction 36 a of the insulator 36,steps 74 c for being arranged approaching pipes 48 a and returning pipes48 b (FIG. 9) of cooling pipes for an end face of circumferentialdirection 48 are formed. Furthermore, on an inner surface 36 c of theinsulator 36, several recesses 76 extending to axial direction atspecified circumferential direction intervals. The heaters 38 are placedinto the recesses 76. (FIG. 3)

In a state that the insulator 36 is arranged in the inner side of thehousing 34, as shown in FIG. 8, the cover fixing pieces 44 b of theradial direction separation preventing members 44 are arranged as toface to the end faces of circumferential direction 36 a of the insulator36 and the housing fixing pieces 44 a of the radial direction separationpreventing members 44 are arranged at the steps 74 a of the insulator36. Therefore, no gap is generated between the housing 34 and theinsulator 36.

The heaters 38 (FIG. 3) are bar or line resistance heaters. And theheaters 38 are uniformly-distributed on the inner surface 36 c of theinsulator 36. These heaters 38 are electrically connected to terminals(not shown) arranged on the outer surface of the housing 34. Theterminals supply power to the heaters 38 in-use.

The seals 40 are cords made of quartz fibers. As shown in FIG. 6 andFIG. 7, the seals 40 are arranged with extending to axial directionbetween the inner surfaces of both ends of circumferential direction ofthe insulator 36 and the outer surfaces of both ends of circumferentialdirection of the isothermal material 42, between a central portion ofthe inner surface of the insulator 36 and a central portion of the outersurface of the isothermal material 42. Consequently, gaps between theinsulator 36 and the isothermal material 42 at the both ends ofcircumferential direction cause the diffusion of the metal impurities tobe prevented from the inner surface of the insulator 36 into the heatingchamber S1 through the gaps. And the seals 40 prevent the insulator 36from contacting directly to the isothermal material 42. As a result, theinsulator 36 and the isothermal material 42 are kept from damaging bycontacting each other.

The isothermal material 42 is semi-cylindrical heat-resistant glass suchas quartz glass or the like. And the isothermal material 42 constructsthe inner wall of the heating chamber S1 and is heated uniformly withheat from the heaters 38. The end surfaces of circumferential direction42 a of the isothermal material 42, as shown in FIG. 9, are set to besame level to the end faces of circumferential direction 36 a (the step74 c) of the insulator 36.

The heat-resistant glass for the isothermal material 42 is no diffusionof metal impurities and high heat-resistance. Consequently, theconstruction that the isothermal material 42 is arranged in the innerside of the insulator 36 and the heaters 38 prevents the diffusion ofthe metal impurities from the insulator 36 into the heating chamber S1,the diffusion of the metal impurities from the isothermal material 42itself, and radiates the heat from the heaters 38 to the heating chamberS1 through the isothermal material 42 uniformly.

The end face of circumferential direction covers 46 prevent the metalimpurities from the insulator 36 from diffusing into the heating chamberS1 with covering the end faces of circumferential direction 36 a of theinsulator 36. As shown in FIG. 6 and FIG. 9, each of the end face ofcircumferential direction covers 46 is band-shaped high heat-resistantand low heat-diffusion material such as titanium or the like. A cut-out78 for preventing from contacting to the support 54 a is arranged at theportion in a longitudinal direction of each of the end face ofcircumferential direction covers 46 that faces to the end face ofcircumference direction 42 a of the isothermal material 42. Holes 80 forscrews 70, as shown in FIG. 9, are prepared on the places thatcorrespond to the screw holes 72 on the radial direction separationpreventing member 44.

The holes 80 are elongate holes which are elongated in a longitudinaldirection of the end face of circumferential direction covers 46.Consequently, the end face of circumferential direction covers 46 can beadjusted in its longitudinal direction after the screws 70 are fastenedto the screw holes 72 on the radial direction separation preventingmembers 44.

When the end face of circumferential direction covers 46 are fixed tothe radial direction separation preventing members 44, one end of widthdirection of each of the end face of circumferential direction covers46, as shown in FIG. 9, is arranged on a surface of the cover fixingpiece 44 h of the radial direction separation preventing member 44. Andthe other end of width direction of each of the end face ofcircumferential direction covers 46, as shown in FIG. 3 and FIG. 9, isbended in a direction to approach the end face of circumferentialdirection 42 a of the isothermal material 42 as to face to the end faceof circumferential direction 42 a. The end face of circumferentialdirection covers 46 cover not only the end faces of circumferentialdirection 36 a of the insulator 36 but gaps S3 (FIG. 9) between theinsulator 36 and the isothermal material 42. As a result, the metalimpurities diffused from the insulator 36 are prevented from diffusinginto the heating chamber S1 steadily.

The cooling pipes for end face of circumferential direction 48 are“pipes for passing water” constructed by bending high heat-resistant andlow heat-diffusion pipes (titanium or the like) substantially “U”-letterin shape. As shown in FIG. 6 and FIG. 9, the cooling pipes 48 arearranged to extend the entire length of the end face of circumferentialdirection 36 a between the end faces of circumferential direction 36 aof the insulator 36 and the end face of circumferential direction covers46. In other words, the approaching pipes 48 a and the returning pipes48 b of the cooling pipes for end face of circumferential direction 48are set parallel each other and contacted to the steps 74 c of the endfaces of circumferential direction 36 a. Bending portions 48 e (aboarder of the approaching pipe 48 a and the returning pipe 48 b) of thecooling pipes 48 (FIG. 6) are arranged at one end of longitudinaldirection of the end faces of circumferential direction 36 a. Both ends48 c, 48 d of the cooling pipes 48 are stuck out through the cut-out 68of the housing 34 at the other ends of longitudinal direction of the endfaces of circumferential direction 36 a.

The cooling pipes for end face of circumferential direction 48 and theend face of circumferential direction covers 46 may be set separately.In this embodiment, the cooling pipes for end face of circumferentialdirection 48 are welded on the reverse of the end face ofcircumferential direction covers 46. Consequently, a positioning of thecooling pipes 48 for end face of circumferential direction 48 and afixing of the end face of circumferential direction covers 46 to theradial direction separation preventing members 44 can be done at onetime. As a result, the positioning of the cooling pipes 48 can be easilydone. And the end face of circumferential direction covers 46 can becooled efficiently with the cooling pipes for end face ofcircumferential direction 48.

The axial direction separation preventing members 50 prevent theinsulator 36 from separating to axial direction by contacting to the endfaces of axial direction 36 b of the insulator 36. As shown in FIG. 7,each of the axial direction separation preventing members 50 includes acontact board 82 contacting to the end face of axial direction of theinsulator 36 and a contact piece 84 rising up at rights from outer edgeof the contact board 82. The contact board 82 is substantially“U”-letter in shape. An outer diameter of the contact board 82 issubstantially the same as an inner diameter of the housing 34. And asshown in FIG. 10, a step is prepared at an end face of circumferentialdirection 82 a of the contact board 82. An outer part of the end face ofcircumferential direction 82 a is set the same level as the end face ofcircumferential direction 34 a of the housing 34. An inner part of theend face of circumferential direction 82 a is set the same level as theend face of circumferential direction 36 a, 42 a of the insulator 36 andthe isothermal material 42 respectively. The contact board 82 includesseveral holes of screw 88 which are fastened with several fixing screws86 (FIG. 7) and several holes of screw 92 which are fastened withseveral fixing screws 90. After inserting the contact piece 84 (FIG. 7)into a gap S4 between housing 34 and the step 74 b (FIG. 6 and FIG. 8)of the insulator 36, this contact piece 84 is welded to the housing 34.

Each of the fitting plates 52, as shown in FIG. 7, has a half-roundcut-out 94 on a part of a board. Each of the fitting plates 52 includesseveral holes 96 which are fastened with several fixing screws 86,several holes of screw 100 which are fastened with several fixing screws98 (FIG. 13 and FIG. 14), and several holes 104 through which severalfixing screws 102 pass (FIG. 5). The fitting plates 52 are fixed to theaxial direction separation preventing members 50 with the fixing screws86.

In addition, as shown in FIG. 2 and FIG. 5, shapes of the fitting plates52 for the semi-cylindrical furnaces 26 a and 26 h are different eachother. The shape of the fitting plate 52 for one semi-cylindricalfurnace 26 a is corresponded to the shape of the support 30. The shapeof the fitting plate 52 for the other semi-cylindrical furnace 26 b isconsidered as to keep an area for a fixing part 106 for fixing thehydraulic cylinder 32.

The supports 54 a and 54 b are for supporting the edge of axialdirection of the isothermal material 42. The shapes of the supports 54 aand 54 b are selected depending on the shape of places to be supported.

The supports 54 a support the edge of axial direction of the isothermalmaterial 42 at its edge of circumferential direction. As shown in FIG.11 and FIG. 12, each of the supports 54 a includes a fixing plate 108fixed to the axial direction separation preventing member 50, supportingplate 110 a set at rights against the fixing plate 108 and arranged asto face to the inner surface 42 c of the isothermal material 42, andsupporting plate 110 b set at rights against the fixing plate 108 andthe supporting plate 110 a, and arranged as to face to the end face ofcircumferential direction 42 a of the isothermal material 42. Each ofthe fixing plates 108 has several holes 112 though which the fixingscrew 90 pass.

The supports 54 b support the edge of axial direction of the isothermalmaterial 42 at other than its edge of circumferential direction. Asshown in FIG. 11 and FIG. 12, each of the supports 54 b includes afixing plate 108 fixed to the axial direction separation preventingmember 50, supporting plate 110 a set at rights against the fixing plate108 and arranged as to face to the inner surface 42 c of the isothermalmaterial 42. And the shape of each of the supports 54 b is substantially“L”-letter with the fixing plate 108 and the supporting plate 110 a.Each of the fixing plates 108 has several holes 112 though which thefixing screw 90 pass.

In addition, the holes 112 of the supports 54 a and 54 b can be mere“circular form”. But it is preferred that the holes 112 are “elongateholes”, because the supports 54 a and 54 b will be adjustable. If theholes 112 are “elongate” to radial direction, the supports 54 a and 54 bwill be adjustable to radial direction of the isothermal material 42. Asa result, the isothermal material 42 will be supported steadily.

Furthermore, the material for the supports 54 a and 54 b is not limited.But to prevent metal contamination of the raw material silicon 12, it ispreferred to use high heat-resistant and low heat-diffusion materialsuch as titanium or the like.

The side panel cooling pipes 56 are “pipes for passing water” made ofhigh heat-resistant and low heat-diffusion pipes (titanium or the like).As shown in FIG. 7 and FIG. 11, the side panel cooling pipes 56 arearranged as to contact to all of the supports 54 a and 54 b. In otherwords, the side panel cooling pipes 56 are arranged along the outer edgeand the edge of circumferential direction of the insulator 36 and theinner circumferential edge of the isothermal material 42. The both ends56 a and 56 b of the side panel cooling pipes 56 are stuck out at thecenter part of the housing 34.

The supports 54 a, 54 b and the side panel cooling pipes 56 can bearranged independently each other. But in this embodiment, the sidepanel cooling pipes 56 are welded to the fixing plates 108 of thesupports 54 a and 54 b. Consequently, a positioning of the cooling pipes56 and a fixing of the supports 54 a and 54 b to the axial directionseparation preventing members 50 can be done at one time. As a result,the positioning of the cooling pipes 56 can be easily done. And thesupports 54 a and 54 h can be cooled efficiently with the cooling pipes56.

The side wall members 58, as shown in FIG. 7 and FIG. 14, cover the endfaces of axial direction 36 b of the insulator 36 from the surfaces ofthe axial direction separation preventing members 50 and the fittingplates 52. And the side wall members 58 construct the inner wall of theheating chamber S1. The shape of each of the side wall members 58 ishalf-disc shape and the side wall members 58 are made of heat-resistantglass such as quartz glass or the like. The side wall member 58 for onesemi-cylindrical furnace 26 a has a circular cut-out 116 for leading outthe wire connector 18 c of the basket 18 placed in the heating chamberS1.

The covers 60, as shown in FIG. 7 and FIG. 14, cover the side wallmembers 58. Each of the covers 60 includes a half-disc shape cover plate118 arranged to face to the side wall member 58 and a circumferentialwall 120 constructs a space S5 for placing the side wall member 58. Thecover plate 118 has a circular cut-out 122 corresponds to the cut-out116 for the side wall member 58. And on outer edge of the cover plate118, several holes for screws 124 (FIG. 7) to which the fixing screws 98are fixed are prepared. Substantially “L”-letter shaped brackets 126 arefixed on inner circumferential surface of the circumferential wall 120.And the side wall member 58 is fixed to the brackets 126.

A cover (not shown) for covering the cut-out 122 of the cover 60 may beattached to open and close the cut-out 122.

The fixing brackets 62, as shown in FIG. 14, are for fixing the covers60 and the side wall members 58 to the fitting plates 52. Each of thefixing brackets 62 is constructed as to be substantially “Z”-lettershape by connecting two fixing plates 128 a and 128 b with connectingplate 130. Each of the fixing plates 128 a and 128 b has a hole forfixing screw 98 (not shown). One fixing plate 128 a is fixed to thecover 60 with the fixing screw 98 and the other fixing plate 128 b isfixed to the fitting plate 52 with the fixing screw 98.

According to this embodiment, the heat of the heaters 38 is preventedfrom transferring directly to the housing 34 by the insulator 36 and theend faces of circumferential direction 36 a and the end faces of axialdirection of the insulator 36 are cooled by the cooling pipes for endface of circumferential direction 48 and the side panel cooling pipes56. Consequently, the deforming by heat expansion of the housing 34 andthe insulator 36 is prevented. And preventing from generating a gap at ajoint surface between the two semi-cylindrical furnaces 26 a, 26 bcauses a leak of the heat of the heating chamber S1 through the gap anda breakage of the heaters 38 by avoiding “bending stress” from innersurfaces of the recesses 76 (FIG. 3 and FIG. 6) to the heaters 38 to beavoided.

1-5. (canceled)
 6. A silicon heating furnace having a heating chamber for containing raw material silicon to be heated, comprising: two semi-cylindrical furnaces constructing the cylindrical silicon heating furnace by combining each other; each of the semi-cylindrical furnaces having: a semi-cylindrical housing; a semi-cylindrical insulator arranged in inner side of the housing; a heater arranged in inner side of the insulator; a semi-cylindrical isothermal material made of heat-resistant glass, and arranged in inner side of the heater and heated by the heater, and constituting an inner wall of the heating chamber; radial direction separation preventing members arranged in inner side of both ends of circumferential direction of the housing, and preventing a separation of the insulator to radial direction by contacting at end faces of circumferential direction of the insulator; end face of circumferential direction covers fixed on the radial direction separation preventing members, and covering the end faces of circumferential direction of the insulator; and cooling pipes for end faces of circumferential direction through which cooling water passed arranged between the end faces of circumferential direction of the insulator and the end face of circumferential direction covers.
 7. The silicon heating furnace according to claim 6, wherein both of the end face of circumferential direction covers and the cooling pipes for the end face of circumferential direction are made of titanium and welded each other.
 8. The silicon heating furnace according to claim 6, further comprising seals made of string of quartz fibers arranged toward axial direction between an inner surface of the end of circumferential direction of the insulator and an outer surface of the end of circumferential direction of the isothermal material.
 9. The silicon heating furnace according to claim 6, wherein each of the two semi-cylindrical furnaces comprises axial direction separation preventing members arranged at both ends of axial direction of the housing, preventing the insulator from being separated toward the axial direction by contacting to both end faces of axial direction; supports having fixing plates fitted to the axial direction separation preventing members and supporting plate supporting the end of axial direction of the isothermal material; side panel cooling pipes through which cooling water pass; side wall members made of heat-resistant glass, covering the end faces of axial direction and constituting inner walls of the heating chamber.
 10. The silicon heating furnace according to claim 7, wherein each of the two semi-cylindrical furnaces comprises axial direction separation preventing members arranged at both ends of axial direction of the housing, preventing the insulator from being separated toward the axial direction by contacting to both end faces of axial direction; supports having fixing plates fitted to the axial direction separation preventing members and supporting plate supporting the end of axial direction of the isothermal material; side panel cooling pipes through which cooling water pass; side wall members made of heat-resistant glass, covering the end faces of axial direction and constituting inner walls of the heating chamber.
 11. The silicon heating furnace according to claim 8, wherein each of the two semi-cylindrical furnaces comprises axial direction separation preventing members arranged at both ends of axial direction of the housing, preventing the insulator from being separated toward the axial direction by contacting to both end faces of axial direction; supports having fixing plates fitted to the axial direction separation preventing members and supporting plate supporting the end of axial direction of the isothermal material; side panel cooling pipes through which cooling water pass; side wall members made of heat-resistant glass, covering the end faces of axial direction and constituting inner walls of the heating chamber.
 12. The silicon heating furnace according to claim 9, wherein the supports and the side panel cooling pipes are made of titanium and welded each other.
 13. The silicon heating furnace according to claim 10, wherein the supports and the side panel cooling pipes are made of titanium and welded each other.
 14. The silicon heating furnace according to claim 11, wherein the supports and the side panel cooling pipes are made of titanium and welded each other. 